The present invention relates to networking. The present invention is especially applicable to controlling errors in the providing of content to multiple users, especially video content across broadband digital networks, especially residential broadband networks, such as cable or satellite TV networks.
With the slow but steady deployment of broadband residential networks, delivering high-quality digital video to a large number of simultaneous users becomes feasible. Examples include interactive video-on-demand and digital video multicasting or broadcasting. To compete with the conventional video delivery media (e.g. VCR tapes, LD, and DVD), these services not only have to be cost-effective and convenient, but also have to achieve competitive video quality.
Unlike the Internet, which is an extremely error-prone environment with little or no performance guarantees, broadband residential networks generally have higher bandwidth, lower latency, lower loss, and the performance is relatively stable. Nonetheless, occasional data losses in such networks are inevitable and would certainly result in video-quality degradations at the receiver end. While it is generally acceptable to receive lower-quality video over the Internet, consumers would be much less tolerant of degradation of video delivered over broadband residential networks where high-quality video is the norm (e.g. TV broadcast and cable TV) rather than the exception.
The general problem of error control is not new and has been studied extensively over more than two decades. Traditionally, there are two major classes of error-control algorithms: retransmission-based algorithms, commonly known as Automatic Repeat Request (ARQ), and redundancy-based algorithms, commonly known as Forward Error Correction (FEC). In ARQ, lost packets are transmitted repeatedly until correctly received by the receiver. In FEC, additional redundant data are injected into the data stream so that errors or erasures can be corrected at the receiver.